The present invention relates to a fluidized-bed activation furnace for activated carbon. In the conventional process for activating carbon, a rotary kiln, a moving-bed reaction apparatus, a fluidized-bed reaction apparatus, etc. are used. Among these, the fluidized-bed reaction apparatus is excellent in that the heat exchange rate is so high as to make the temperature of the whole carbon granules uniform, thereby producing a uniform product in quality especially in batch-wise operation.
In any type of the apparatus, however, the reaction temperature is so high as 800.degree. to 1000.degree. C. that contact reaction of the carbon granules with a large amount of steam is necessary. It is also necessary to cool the product by some method in order to discharge it from the reaction apparatus. In the rotary kiln and the moving-bed reaction apparatus, the activation reaction and cooling are ordinarily continuous. On the other hand, the fluidized-bed reaction apparatus can be used both as a continuous apparatus and as a batch-wise apparatus. In the case of a batch-wise apparatus, the residence time is uniform and it is possible both to obtain a product having a uniform reaction rate and to obtain various products of different qualities by varying the reaction rate for each batch. However, unlike a continuous apparatus, since a batch-wise apparatus must raise and lower the temperature of the activation furnace itself at every activation, there is much loss of time and energy. In addition, repeating Temperature-rising and-falling of apparatus is apt to produce a problem of deterioration of the apparatus. Since a part of a lift valve for discharging the granules of product from the bottom portion of a conventional reactive layer is exposed to a high temperature fluidized-bed and the structure requires the valve to be installed at a height of at least several ten mm above the perforated plate, the product granules which are below the valve in the activation furnace are difficult to be discharged (see FIG. 4). These granules remain in the next batch and will be activated twice. It will cause nonuniform product.
As a result of researches undertaken by some of the present inventors so as to solve these problems, a fluidized-bed activation furnace was developed which comprises a central hollow pillar vertically extending from the bottom portion of the fluidized-bed activation furnace to the central portion of the furnace, a bowl-shaped cap covering the top portion of the central hollow pillar, a perforated plate located under the bowl-shaped cap and fixed to the outer periphery of the central hollow pillar below an outlet for discharging activated carbon granules so as to divide the activation furnace into two portions of a upper portion and a lower portion, a steam jacket and a fire resistant and heat insulating material covering the outer periphery of the central hollow pillar, a cooling steam introducing system, and a high temperature activating gas introducing system which is provided at the lower portion of the furnace (refer to "Kagaku Sochi", the May number (1975), pp. 38 to 44).
The present inventors further studied on this fluidized-bed activation furnace and, as a result, it has been found that it is possible to discharge substantially the whole amount of activated carbon granules in a short time maintaining the high temperature without leaving almost any activated carbon granules on the perforated plate by controlling (i) the opening ratio of the perforated plate and (ii) the angle of inclination of the perforated plate respectively in a specified range, thereby shortening the cycle time per batch. The present invention has been achieved on the basis of this finding.
Accordingly, it is an object of the present invention to eliminate the above-described problems in the prior art and to provide a fluidized-bed activation furnace for carbon in which substantially the whole amount of activated carbon granules can be discharged in a short time maintaining the high temperature after the activation of granules of active carbon forming a fluidized-bed of the activated carbon granules.